1. Field of the Invention
The present invention relates in general to a heat exchanger that includes a plurality of relatively thin core plates of aluminum alloy or the like that are stacked on one another to constitute a core unit.
2. Description of the Related Art
In order to clarify the present invention, two conventional heat exchangers of the above-mentioned type will be briefly described in the following.
One is a heat exchanger that is disclosed and described in Laid-open Japanese Patent Application (tokkai) 2002-332818. The heat exchanger of this publication comprises a plurality of core plates that are stacked on one another to constitute a heat exchanging core unit, and a bottom plate that is thicker than each core plate and has the heat exchanging core unit tightly mounted thereon through brazing. The stacked core plates are constructed to form both oil passages and cooling water passages which are alternately arranged. Upon usage of the heat exchanger, the bottom plate is fixed to a partner member or device.
The other one is a heat exchanger that is disclosed and described in Laid-open Japanese Patent Application (tokkai) 2006-17430. The heat exchanger of this publication comprises a plurality of core plates that are stacked on one another to constitute an oil flow core unit in which only oil flow passages are formed, and a housing that receives therein the oil flow core unit leaving therebetween cooling water passages. The publication shows a modification of the heat exchanger in which a bypass oil passage extends from an oil inlet port to an oil outlet port bypassing the oil flow core unit. The bypass oil passage extends horizontally between a top face of the oil flow core unit and an upper part of the housing.